R3ZZ (I.D.=3/16', O.D.=1/2', Thickness=10/51') r3z bearings are shielded on BOTH SIDES to keep lubricant in Chromium Steel long-life bearings, smooth and low noise ABEC Tolerance 3 (P6), Z1 Noise Level for most general use Static load rating of 488 newtons and dynamic load rating of 1301 newtons